snips.........

Really the concept is sort of  backwards -
 you need the diameter for slow speeds - take off
and climb - the disk area losses  get
 lower at higher speeds - particularly at cruise,
where you have reduced the disk
 loading by reducing engine power (potential
efficiency goes up). If you  have  variable
 pitch, you dial in your "square" or "over square"
, and "it don't get  much better  than this"
 Vance

Vance is right, I finally understand this after years
of thinking that prop
efficiency is directly related to diameter.  What it
is  *actually* related
to is  the mass of air through the prop verses the
thrust produced.   A very
short prop can be efficient if the air speed is high.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org